And yes that includes me.
For those who don’t know, RFC1918 is the Internet standard that allocates the addresses used for private networks – 10/8, 192.168/16, or 172.16/12.
And in reference, specifically :-
To minimize the risk it is strongly recommended that an organization using private IP addresses choose randomly from the reserved pool of private addresses
(Apologies for the incorrect spelling above; it’s a quote from an American source)
This was reinforced to me yesterday whilst I was working from home, and I had trouble with a site-to-site VPN joining my network to work’s. As it happens there was no addressing conflict, but I had to install many routes more than should be necessary.
And I keep seeing this sort of thing; joining multiple networks when everybody is using 10/8 is a continual game of chicken – when are we going to find ourselves in conflict?
Of course there is a “fix” for this – NAT. The real fix of course is to use global IPv6 addresses even for devices and networks that will never be on the global Internet.